The Maine Center for Disease Control and Prevention and the Maine Department of Agriculture, Conservation and Forestry have announced that a horse euthanized due to neurologic signs last week in Oxford County tested positive for Eastern equine encephalitis (EEE). The horse was vaccinated for EEE and West Nile virus (WNV) a year ago, but had not received a booster dose.

EEE is a virus that is transmitted through the bite of an infected mosquito. Eight pools of mosquitoes have tested positive for EEE in York County this year. Maine last saw EEE in horses in 2009, when 15 horses died of the disease.

"EEE, which is carried by mosquitoes, is a fatal, viral disease in horses," Michele Walsh, DVM, state veterinarian said. "The virus can affect human beings if they are bitten by mosquitoes that carry the virus. People cannot acquire EEE infection from sick animals, only from the bite of an infected mosquito."

EEE virus is carried by mosquitoes, which pick it up from infected wild birds. The virus replicates in birds, which act as natural reservoirs for the disease.

Signs of the disease in horses include stumbling or poor balance, unusual behavior, and lethargy. Other signs include head pressing, circling, tremors, seizures, and eventual coma.

“EEE is preventable in horses through vaccination,” Walsh advised. “If more than six months has elapsed since a horse has been vaccinated, a booster vaccination may be needed.”

A different vaccination can also protect against WNV, which has not been detected in Maine so far in 2013, but was detected in 2012, and has been detected in our neighboring